Expanding drill



UNITED STATES' PATENT OFFICE.

WILLIS CLARK, 0F BUFFALO, NEW YORK, AASSIGN OR OF ONE-HALF TO CHARLES D.

CLARK, 0F BUFFALO, NEW YORK.

EXPAN DING DRILL.

specification of Letters Patent.

Patented Nov. 2, 1920.

To all whom it may concern.'

Be it known thatI I, lVILLIs CLARK, a citiaen of the United States, residing at Buffalo` 1n the county of Erie and State of New York, have invented a new and useful Improvement in Expanding Drills, of which the following is a specification.

This invention relates to improvements 1n expanding drills,| and more particularly to that sort which are used in coal mining to produce an enlarged pocket or chamber at the inner end of a blast hole made by the ordinary non-expanding drill. This pocket or chamber enables a larger charge of explosive to be used in a bore of given length and makes it possible to better concentrate and control the blast than if a hole of uniform diameter throughout is used. ln expanding drills as heretofore made,the cutting blades are `not adequately supported or braced against the severe twisting strain to which they are subjected in use and which tend to bend and loosen them or break their pivotal connections, thereby destroying the utility of the drill. ln some of the prior drills the parts are so proportioned that they leave an outwardly projecting portion of the rock in the bottom of the hole, and

in others, a central hole of smaller diameter than the rest of the cavity which is caused by an elongated center-bit. ln such cases it is impossible to pack the blasting charge evenly and tightly.

One object of the inventionl is to overcome this diiiiculty by providing cutting blades which are relatively wide and are mounted in a head in a novel manner such that rigid portions of the head overlap the cutting blades on their outer sides, thus taking a considerable amount of the twist strains and protecting them from injury from the causes mentioned. Another object is to provide a strong and simple expanding drill in which the pivoted blades can be readily removed and replaced. Another object is to so proportion the cutting members of the drill that the chamber or pocket out thereby will have a substantially smooth and level side wall and end wall or bottom.

In the accompanying drawings:

Figure 1 is a plan view of a drill embodying the invention, showing the blades in their closed position and inserted in a bore of uniform diameter throughout.

Fig. 2 is a similar view showing the drill expanded and in place in the enlarged cavity made thereby. j

Fig. 3 is a sectional plan view on line 3 3, Fig. 5, showing the parts in the same relative positions as in F ig. 2.

Fig. 4 is a transverse sectional elevation on line 4-4, F ig. 3.

Fig. 5 is a side elevation, with the cutting blades retracted.

A is the usual blast hole as made by an ordinary nonexpanding drill and B is the pocket or chamber at the end thereof which is made by means of the expanding drill hereinafter described. The expanding drill is preferably constructed as follows:

C is a head or supporting member for the swinging cutting blades 10 and 10'L1 which are disposed on opposite sides of the axis of the drill. The head is preferably constructed of an integral or solid metal block or body portion 11 which is riveted or otherwise secured to an attaching portion osocket 12 adapted for attaching the drill to a shank' or rod of any suitable sortfor rotating the drill. The body portion 11 of the head C is provided with two o-uter forwardly extending [iat faced webs or parts 13, 14 and a flattened intermediate or central web or part 15 located on the axial line of the drill, the two outer webs 13, 14 being spaced eqfiidistant on opposite sides thereof. This construction provides two recesses 16 for the reception of the cutting blades 10, 10a. The transverse dimension of these recesses 16 is substantially equal to the transverse dimension o-f the cutting blades.

The cutting blades are pivotally secured in the recesses 16 by bolts or the like 17, 18 passing through registering holes 19, 20 in the blades 10, 10*l respectively and in the head. The pivot hole fo-r each blade is located adjacent the rear end thereof. Consequently'a greater leverage is exerted upon the blades because the tips of the blades engage the inner end of the hole at a greater distance laterally from the pivots of the blades than would be the case if the blades werepivoted centrally of the axis of-the head and of the blades. rllherefore, the

blades, pivoted as described quickly spread ting edges 25, which, as shown,

ing the pivot hole, with ay curved slot 22 con-- centric with its pivot, and the pivot bolt of the other blade passes through this slot. rlhis enables a very wide blade to be used which, together with the short length of said blade, insures a maximum of strengt Screw bolts or other removable bolts or pins are preferably used for the blade pivots so that the blades can be readily removed for sharpening them or for thesubstitution of new blades.

Each of the recesses 16 is preferably provided with a diagonally disposed inner end wall 23 extending rearwardly away from the pivot of the blade located in said recess. These diagonalA walls form strong rigid stops or abutments for the cutting blades, to limit their outward swing and determine the diameter of the pocket. The blades are prevented from swinging in the opposite direction beyond the closed position shown in Figs.l 1 and 5, with their side cutting edges substantially parallel to 'each other and to the sides of the head, by the engagement of the pivot bolts of the blades with the rear 'ends of the slots 22. V

For properly centering and guiding the drill in operation, the central web or part 15 of the head is prolonged into a centeringbit 24 having two oppositely inclined cutorm a Wide, blunt cutting member.

rlhe forward cutting edges of the pivoted blades are preferably so curved and bent outwardly as to coperate with the cen.

tering bit 24 to form an even and level bottom or inner end in the pocket` which is desirable as it enables the blasting charge to be packed closely and `evenly against all the Walls of the pocket, thereby -realizing the maximum effect from the blast.

It will be seen from the drawings that the wide cutting blades, 10, 10a, being mounted between the overhanging webs 13, 14 and 15, form an exceedingly strong, rigid construction which will prevent the drill from being damaged or weakened by the twist strains to which it may be subjected in use..

l claim as my invention:

1. An expanding drill comprising a head, a pair of cutting blades o1 substantially the same width as the head, said head having rigid webs engaging opposite sides of each blade, andv a separate extending through said webs, ing located at opposite sides of the axis of the head and the pivot for each blade crossing the plane in which the other blade swings each of said blades being adapted to swing across said axis to the side opposite its pivot.

2. An expanding drill comprising a head and a pair of swinging cutting blades, each mounted on a separate pivot, which pivots are located at opposite sides of the axis of said head and adjacent the sides thereof, said head having two outer webs and a central web between which said swinging blades are pivotally mounted and thrpugh which said pivots pass, said central web forming a center-bit having a wide outer end with cutting edges which coperate with said cutting blades to cut 'a pocket with a substantially flat bottom wall.

3.' An expanding drill comprising a head having a rigid lcentral web forming a center cutter and rigid side webs at opposite sides of said center web, a pair of swinging cutting blades disposed at opposite sides of said center cutter and confined between the same and said side webs, a separate pivot for each blade extending through saidI webs,

said pivots besaid pivots being located at opposite sides of the axis of the head, and each of said blades having a slot through which the pivot for the other blade passes.

3rd day of Oct.,

Witness my hand this 4 l WILLIS CLARK. Witnesses:

JOHN H. ILLIG, l CHARLES L. HrsLor.

pivot for each blade 

